diff --git a/pdfminer/pdfdocument.py b/pdfminer/pdfdocument.py
index cfa5160..5fb9cce 100644
--- a/pdfminer/pdfdocument.py
+++ b/pdfminer/pdfdocument.py
@@ -587,6 +587,8 @@ class PDFDocument(object):
             if settings.STRICT:
                 raise PDFSyntaxError('Catalog not found!')
         return
+    
+    KEYWORD_OBJ = KWD(b'obj')
 
     # _initialize_password(password=b'')
     #   Perform the initialization with a given password.
diff --git a/samples/nonfree/175.pdf b/samples/nonfree/175.pdf
new file mode 100644
index 0000000..d5df923
Binary files /dev/null and b/samples/nonfree/175.pdf differ
diff --git a/tests/test_tools_pdf2txt.py b/tests/test_tools_pdf2txt.py
index 9292b78..70e6cf9 100644
--- a/tests/test_tools_pdf2txt.py
+++ b/tests/test_tools_pdf2txt.py
@@ -50,5 +50,8 @@ class TestDumpPDF():
  
     def test_8(self):
         run('../samples/contrib/','2b','-A -t xml')
+
+    def test_9(self):
+        run('../samples/nonfree/','175') # https://github.com/pdfminer/pdfminer.six/issues/65
 if __name__ == '__main__':
     nose.runmodule()